A new normal?

Thousands of concertgoers celebrated the end of a country music festival in Las Vegas. Not only were they drawn by the music, they were drawn by all the attractions of Las Vegas itself.

About 22,000 of them crowded in the shadows of several enormous hotels. It was a time for some fun.

Suddenly, what sounded like automatic gunfire broke out. Many concertgoers at first thought the noise came from fireworks. The lead singer continued singing until he realized what was happening. Gradually, too, the crowd became aware of the shooting.

The gunfire reportedly lasted more than nine minutes.

The shoot...